There are three major factors to consider when sailing the South African Coast:
The Currents
The Weather
The Ports, anchorages and coastal dangers
Each one of these needs to be considered in planning a safe trip.
The Currents The currents on the Eastern South African coast consist of the warmMozambique, also known as the Aghulas Current, which flows in a South Westerly direction down the coast and reaches speeds of up to 5 knots, and the counter current which flows much weaker, and very close to shore in a North Easterly Direction up the coast. The danger on the coast is that the SW gales that blow frequently up the coast, (known locally as the “buster”), blow in the opposite direction to the current building up big, and I mean BIG steep seas, Add to this the continental shelf which is very close offshore, and that the current flows strongest just to seaward of the shelf, and you have three elements that combine to form some very dangerous “freak” waves that have damaged and/or sunk big ships. When coming down the coast from the Mozambique boarder to Cape Town it is good to keep in the current to get the benefit of it, but should the wind turn to SW and become a gale, you need to get out of the current, the options are to head close inshore or right out to sea, and this could be up to 100 NM offshore.
1) Heading inshore means you will have to beat down the coast in a series of very short tacks; this is not a good idea if short handed.
2) Heading out to sea, up to 100nm off shore, could mean a long haul across the current again to get back to a port should you have a problem.
When crossing the current coming in from Madagascar, Mauritius or Reunion, then try not to cross the current if a SW gale is immanent, rather run down out side of it and run back up until it is passed. Mark time as it were
On the coast between Cape Vidal and St Lucia and then theTranskei(WildCoast) and Eastern Capecoasts between Port Edward andCapePadrone, also known as the Wild coast is where the current runs the closest inshore and is the strongest, often running at 5 knots. The current runs strongest just on the outside of the 200meter depth contour and can be found by checking the temperature and colour of the water. To be in the current the water temperature should be above 24 degrees and the water a deep blue.
Sometimes the dividing line between the currents is visible by a difference in colour on either side of a very distinct demarcation line.
The strongest current is usually between 10 and 25 miles offshore depending on the 200meter depth contour. In the days before GPS many a boat underestimated the current and ended up inPort Elizabeth, rather than East London. On one Vasco Da Gama race, one of the boats would have won, had it not overshot and ended up in Port Elizabeth instead, much to the embarrassment of the navigator and skipper, but all too easily done in those days. Beyond Bird Island the current tends to sweep S more and not to follow the coast closely as the coast bears to the W. On the way down from Richards Bay or Durban to Cape Town, go on the outside of Bird Island unless you are in a SW gale in which case you need to use Bird Island Passage and stay close to the shore to get smaller seas in what the locals call the “back door to Port Elizabeth” There are other “back doors” on the coast, one is between Cape St Lucia and Richards Bay, tack over the shallow banks and you will make more headway, as the seas are considerably smaller, and keep close inshore from Umlanga Rocks light to Durban. In both cases a sharp eye must be kept for shark nets, and over the banks from Cape Henderson to East London, making sure you clear Nahoon point, the headland before the harbour. The wind affects the current. In a NE wind the current moves inshore, making it virtually impossible to sail up the coast against wind and current. In a SW wind it moves offshore, especially in winter when the cooler counter current gets broad enough for the Sardines to run up to the Natal coast in the annual event called the Sardine run. If a strong SW gale is heading your way then the current often slows down or disappears all together. In which case, head out of the current as the wind is about to hit the fan, literally. There is an insetting or offsetting current in most of the bays from Algoa Bay to Cape Town. Whether it sets you into or out of the bays depends on winds and their strengths. Keep an eye on navigation to ensure you do not get pushed into a bay and have to battle your way out. On the way up the coast the secret is to stay close inshore. Do not go deeper than 20 to 30 meters on the way up from Cape St Francis to the Mozambique border. There are only a few places where I will go to the 30 m contour, Cape Seal at Cape St Francis, between Port Alfred and Riet Punt and at Mbashe River, for the rest I stay on the 20 m line unless I am not making good headway in which case I head to the 10m line and sometimes have to go to the back of the breakers. I have often had to go into 10 meters of water round certain points on theWildCoastto be able to pass the point. Port Edward and South Sands being two of the worst. On the way up you always go on the inside of Bird Island as there is a 2 knot counter current with you there. As you need to catch the SW gales to get up the coast, keep inshore of the SW flowing current if you do not want to damage your boat or worse. I have had a lot of very good sailing trips up and down the coast and although it has a well earned reputation for being dangerous, if you keep these things in mind then it can be a most pleasurable sail. I will tell you the secrets of the weather in the next post.
The red is the warm water of the Mozambique/Aghulas current. The yellow water close inshore is the counter current.
http://www.youtube.com/watch?v=IDPP9eaWTkw
Click on the link for an animation of the current.